Field of the Invention
The present invention relates to a system for harvesting bone graft material for use in bone fusion surgery, including but not limited to fusions of the spine.
Discussion of the Known Art
An object of spinal fusion surgery is to join vertebrae at an affected level of a patient's spine, by inducing the growth of bone tissue that is deposited between the vertebrae during surgery. When fully grown, the deposited bone tissue fuses the vertebrae solidly and permanently. The procedure is long known to reduce or eliminate severe back pain when, for example, an intervertebral disc is damaged or becomes ineffective. See, e.g., U.S. Pat. No. 9,042,960 (May 26, 2015), titled Determining and Placing Spinal Implants or Prostheses, which is incorporated herein by reference.
In a typical fusion procedure, the disc space between the vertebrae is cleaned, and bone or a bone graft material is deposited in the space in a way that allows the material to grow and achieve a healthy fusion. Among available graft materials, bone graft harvested directly from the patient's own bone tissue (autograft) or from a donor, ceramics, bone morphogenic proteins, and/or stem cell based grafts, are frequently used. Of these, autograft obtained from the patient's iliac crest or pelvic area is known to work best to achieve a successful fusion.
Using the patient's own bone tissue as graft material works well to form a confluence of the material with the vertebral bones to be fused. It is also known that (a) the more autograft material used, the greater the likelihood of achieving a successful fusion, and (b) a solid piece of autograft material works better than smaller chips to promote fusion. Basic principles of orthopaedic surgery suggest that an optimum fusion results when a solid piece of bone is inserted to span the entire intervertebral disc space, and when opposite ends of the piece enter or penetrate the vertebral end plates facing the space.
U.S. Pat. No. 7,201,775 (Apr. 10, 2007), incorporated by reference, discloses a procedure that includes implanting a hollow cylindrical stabilizing device (see FIGS. 7 & 8 of the patent) between the end plates the vertebrae to be fused, and rotating the device so it gouges and shears off portions of the end plates which are then forced inside the device. The device has openings so that when oriented as in FIG. 11C of the patent, the sheared bone portions are exposed to the vertebrae through openings in the device in order to promote fusion. The procedure does involve a risk of crushing the end plates and thereby destroying the integrity of the remaining vertebral bone, however. That is, after the end plates are sheared by the device, one or both vertebrae may become prone to fracture and compress into the spinal canal. Also, the device does not work to translocate or displace a solid piece of bone from one vertebra so that an end of the piece enters the body of the other vertebra.
U.S. Pat. No. 8,328,870 (Dec. 11, 2012) describes an interbody fixation system including a cage having a number of blades mounted inside the cage. When the blades are turned not more than 45 degrees as shown in FIGS. 2 and 6C of the patent, the blades bite into the end plates of the opposed vertebrae and fix the position of the cage on and between the end plates. See also, U.S. Pat. No. 7,618,423 (Nov. 17, 2009) which relates to a system for performing spinal fusion including a graft holder assembly, a locking assembly, and a pair of bone graft implants that are introduced into a disc space to effect fusion; U.S. Pat. No. 8,353,912 (Jan. 15, 2013) disclosing an ultrasonic cleaning device for leveling the surfaces of vertebral end plates after the disc space between them is cleaned and before graft material is deposited in the space; and U.S. Pat. No. 8,343,178 (Jan. 1, 2013) describing an ultrasonic saw blade for cutting hard bone without damaging adjacent soft tissue. All relevant portions of the foregoing patents are incorporated by reference.
Notwithstanding known meticulous procedures for obtaining and using autograft material from a patient during surgery, there is no guarantee that a reliable and strong fusion will always be obtained, or that a so-called “non-union” will not occur. A need therefore exists for a system and procedure for obtaining autograft material from a patient during a bone fusion surgery, and for depositing the material between the bones to be fused so that (a) the material spans the space between the bones and also enters the bones, and (b) the material grows rapidly to obtain a healthy, strong, and permanent fusion of the bones.